1. Field of the Invention
The present invention relates in general to vacuum pumps and more particularly to vacuum pumps of the type having a lubricant reservoir holding a liquid lubricant for lubricating and sealing moving part of the vacuum pump.
2. Brief Description of the Prior Art
Many of the vacuum pumps presently available utilize oil for lubrication and sealing against loss of vacuum. Generally, a reservoir of oil is provided and circulated through the vacuum pump stages to lubricate the moving parts of the vacuum pump and to provide a gas seal between the inlet and outlet and various chambers of the vacuum pump.
A well known problem of the prior art concerns contamination of the oil in the oil reservoir. As the vacuum pump operates, gases compressed within the pump liquefy and mix with the oil. The most common contaminating gas is water vapor. After the water vapor is condensed and contaminates the oil reservoir, the oil circulated through the pump cannot properly seal and lubricate the moving parts of the vacuum pump.
In an attempt to solve the water contamination of the oil reservoir some vacuum pumps allow gas to enter and be vented from the compression chamber of the pump reducing the partial pressure of the water vapor. In this manner, less of the water vapor reaches its saturation pressure and condenses within the pump. However, this increases the gas pressure within the compression stroke making the pump less efficient and increasing the temperature of the pump as it operates. Furthermore, even with the gas venting of the compression chamber, water vapor condenses within the oil reservoir so that in prolonged usages of the pump, water builds up and must be drained from the oil reservoir.
Many uses of vacuum pumps require prolonged operation of the vacuum pump. For example, in order to remove water vapor contamination of a refrigeration line, it is often necessary to evacuate the refrigeration line for days at a time. Furthermore, whether the vacuum pump utilizes a vented exhaust or not, operation for this amount of time has required that the pump be monitored intermittently to insure that water contamination does not destroy the pump. This has generally required service personnel to visit the pump every few hours to check the oil level within the pump which indicates whether or not water contamination is occurring. When the oil level reaches a dangerous height, water which has accumulated at the bottom of the reservoir is drained by means of a manual valve.
As can be seen, monitoring of the vacuum pumps is expensive and undesirable. While there have been a wide variety of devices utilized for separating oil and water, no satisfactory device has been found for separating the contaminating water from a vacuum pump as it operates.